Researchers surveyed groups of single men and women who self-reported as either straight, gay, or bisexual to see how often they cross the finish line with a familiar partner.

No surprise: regardless of sexual orientation, guys were more likely to orgasm than women, climaxing 85% of the time. But us ladies were another story: Lesbians were more apt than straight and bisexual women to get there (75% did, compared with 62% and 58%, respectively).

So why is girl-with-girl a more orgasmic combo? Is it a matter of what's happening between the sheets, or physiological differences among the groups? "Like so many aspects of sexuality, the patterns are likely a combination of both biological and cultural factors," says lead study author Justin R. Garcia, PhD, assistant professor of gender studies at The Kinsey Institute at the University of Indiana.

Interestingly, bisexual women and men were least likely to orgasm (though it was only a statistically significant difference for women). That may simply be a factor of the variety of their sexual activities and preferences, according to the researchers, who hope to do more research on whether bisexual women with women are closer to the lesbian group in terms of so-called"success" rates.

As for the study confirming that, yep, men have an easier time of it than women, the scientists weren't surprised. As Garcia puts it: "Men's orgasm rates are likely under strong selective pressure (in evolutionary biological terms) so insofar as orgasm is tied to male ejaculation—which has clear reproductive consequences—we expect that males likely orgasm relatively predictively with familiar partners."

Just don't ask Garcia for secrets to better sex. "I'm firmly in the business of how-come, not how-to," he says.